[1][2] Initially, it was a developer of the tidal power turbines and projects, but after becoming a part of GFG Alliance it has expanded its business also to the waste-to-energy[3] and hydropower.

[6] In February 2014, Atlantis became the world's first tidal energy company to float on the London Stock Exchange's AIM sub-market and commenced construction on MeyGen.

[11] In 2016 the company decided to focus on the most developed sites, so returned the agreement for lease for two potential projects to the Crown Estate, one at Kylerhea between Skye and the Scottish mainland and one at Anglesey Skeries, North Wales.

[16] In 2017, GFG Alliance acquired 49.99% stake in the company in return of the coal-fired Uskmouth power station, which was to be converted to a 220 MW waste-to-energy plant.

[3] In early 2021 the planning was called-in by the Welsh Government for the development of Uskmouth power station, putting the project in doubt.

[22] In October 2022, there was a management buyout of the Advanced Tidal Engineering and Services (ATES) division, along with the associated IP and staff, forming a new company called Proteus Marine Renewables.

In 2022, Proteus Marine Renewables was formed from a management buyout of the Advanced Tidal Engineering and Services division of SIMEC Atlantis, and continues the turbine development.

In 2002, Atlantis Energy tested a 100 kW tidal power device called the "Aquanator" in the straight between San Remo, Victoria and Phillip Island.

[30][33] In July 2008, the AN-400 (or Nereus II) turbine was tow-tested in an open ocean environment, reportedly with record power output and improved water-to-wire efficiency.

[37] By October 2010, the turbine had been installed at the European Marine Energy Centre in Orkney, but developed a blade fault before it could be tested.

[39] The turbine had a single three-bladed rotor, 18 m (59 ft) in diameter, and reached its rated power of 1 MW in a current of 2.65 m/s (5.15 kn; 5.9 mph).

[39] In 2013, Atlantis Resources entered into a partnership with Lockheed Martin to develop and manufacture their next-generation turbine, the 1.5 MW AR1500 for use at the MeyGen project.

[41][42] In January 2021, SIMEC Atlantis deployed a 0.5 MW AR500 tidal turbine in the Naru Strait in the Gotō island chain in southern Japan.

[43] The turbine was designed and manufactured at the Nigg Energy Park in Scotland, before being disassembled and shipped to Japan prior to installation.